Digital technologies will replace analogue systems and deliver greater resilience, security and functionality – potentially at lower cost. However, many of the new digital propositions are proprietary or still in the early stages of their development. Technology selections will therefore be taken on a case-by-case basis.
Among the most mature of the new technologies is the DMR standard, which is composed of three tiers (see DMR box, page 45). DMR Tier III represents the highest-end of the technology which starts withTier I simple, non-licensed walkie-talkie radios. Tier III can provide an alternative to the well-established TETRA standard.
‘In a nutshell, apart from analogue migration, RF power and usage of 12.5kHz channels there isn’t any difference between DMR Tier III and TETRA,’ says Steve Barber, head of product strategy at Sepura.
‘From a functionality perspective for public sector and non-public sector users, TETRA is a lot more advanced. The other thing with TETRA is that it is truly an open standard, whereas DMR isn’t, even at Tier III. At the moment there is some very basic Tier III interoperability going on between Tait and Hytera, but that’s [for] a very basic service. The standard is immature and we expect it to go the same way as Tier II with a small set of features standardised, but beyond that everything is proprietary – including data.’
Andy Grimmett, chief technologist at Simoco, agrees: ‘You definitely can compare TETRA and DMR Tier III,’ he says. ‘The history of [the DMR] standard is very much, feature for feature, like an MPT feature but with traditional TETRA features bolted on including full-featured calling. There’s very little functionality with a TETRA system that isn’t offered by DMR Tier III.’
Others acknowledge the attractions of TETRA’s maturity in spite of the potential for DMR Tier III to suit some users’ needs more closely. ‘TETRA is a mature technology with a lot of features and it was designed for the public sector so the security level is extremely high,’ says GS Kok, VP of the public security and safety department at Hytera. ‘It’s easier to standardise and it already has encryption algorithms so when it comes to IP voice advances, everything is there in the standard.’
It’s early days for DMR Tier III. ‘DMR Tier III is not in a mature state and only one company claims to currently provide Tier III solutions,’ says Trevor Pullen, EMEA TETRA strategy planner at Motorola Solutions. ‘The standard is in a state of flux whereas TETRA has been around for many years. ‘In terms of spectrum, the two are pretty much the same but on the TETRA side you’re really looking at scalability – it scales nationwide with good partitioning for those that require it.’
His colleague Tim Clark, who is product director EMEA for TETRA, points out that DMR Tier III remains a nascent technology. ‘We have our MOTOTRBO solution, which is a DMR standard solution, but our focus remains on Tier II because that’s where the bulk of our business is. We have expanded Tier II to provide trunking and high capacity solutions. We haven’t developed a DMR Tier III solution, firstly because the standard is not mature and there isn’t the ecosystem of suppliers in the market as there is with DMR Tier II. We don’t yet see the requirement for Tier III.’
Another set of technologies that can be compared are dPMR (see dPMR box below) and DMR Tier II. Each has relative merits although dPMR has a smaller number of manufacturers involved.
‘It’s cheaper to manufacture products within the dPMR set of standards but you don’t get the features and benefits you get with DMR,’ adds Motorola’s Clark. ‘The DMR standard has attracted vendors and manufacturers and there is a huge ecosystem of application providers. With MOTOTRBO we have more than 300 application partners to bring value-added applications around services such as health and safety or location-based functionality with GPS.’
‘It’s swings and roundabouts,’ says Sepura’s Barber. ‘You tend to see dPMR priced slightly lower than DMR Tier II, but you have got to be very careful about what you mean by dPMR because few have deployed to standard [specifications]. dPMR is an FDMA technology, so you need a repeater for every 6.25KHz channel compared to a single 12.5KHz repeater in DMR – an equivalent dPMR deployment would require twice the number of repeaters. Then you’d need more RF equipment so the infrastructure cost base for dPMR is probably slightly more expensive.’
That’s offset by potentially lower cost terminals. Kenwood offers its NEXEDGE system based on the NXDN protocol, which is also used by Icom. NEXEDGE is based on dPMR technology, although the system is FDMA and uses 6.25KHz channels. ‘Terminals are lower priced because all that Kenwood and Icom have done is replicate analogue hardware’s form factor,’ says Barber.
‘From the user perspective, DMR products look and feel more attractive, they’ve moved to a TETRA [like] display with full colour and support packet data,’ he adds.
‘Both TETRA and DMR have the ability to have some kind of applications environment to deliver efficiencies and benefits to end user organisations whereas dPMR and NXDN tends to be a direct replacement for analogue radio.’
Kok at Hytera welcomes the potential of dPMR to use spectrum more efficiently but feels there are still regulatory issues that need to be resolved. ‘dPMR is a cute way of splitting 12.5kHz by splitting it into 6.25kHz channels,’ he adds.
‘The only advantage now with dPMR is digitisation, narrow channels and the ability to double up capacity. However, with dPMR you will probably need to immediately apply for a new licence if you want to use both channels in an analogue 12.5kHz band. In addition, while it’s cheap to buy the equipment because it’s a mass market product, it can be very complicated to deploy. DMR is feature-rich, energy-efficient, channel-efficient and plug and play,’ points out Kok.
Grimmett also highlights the regulatory issues associated with dPMR spectrum. ‘The advantage with DMR is that the 12.5kHz channel is the same bandwidth as the analogue set of frequencies so you can put DMR in without frequency replacing. The regulator finds it very easy to allocate frequencies because they’re already in 12.5kHz chunks.
‘For dPMR, however, FDMA technology in one base station uses 6.25kHz frequency and from a regulatory point of view that’s difficult. If a 12.5kHz block is used [to support this] it’s very wasteful because you could end up using just half the available spectrum so DMR really hits the sweet spot.’
Ian Lockyer, marketing manager at Icom highlights issues with maximum allowable power usage. ‘In the US there have been some interference problems where DMR systems are used,’ he says. ‘The Licensing Administration was forced to require DMR users to reduce their power. dPMR does not suffer from this coexistence problem as the frequency bandwidth is lower and can be offset.
'TETRA and other earlier technologies were specifically designed for large system use and as such are not as scalable as the newer technologies. dPMR for example can be as small [a deployment] as two radios talking back to back or scaled to a wide area network with TCPIP interconnection over ADSL and multiple repeaters.’
Beyond that, dPMR suffers from typical early stage technology woes – its development ecosystem isn’t as large as those of rival technologies. ‘An important point for DMR is the amount of support from manufacturers that it has,’ adds Simoco’s Grimmett.
‘There are around 39 members of the DMR Association compared with 14 in the dPMR Association and of those 39, 23 manufacturers are marketing DMR. That’s a key reason why we have developed the DMR route rather than dPMR.’
Lockyer, however, feels that dPMR is the more open standard and it offers less scope for proprietary efforts from vendors. ‘The technology is the same across all the dPMR systems,’ he says. ‘Digital radio technologies have often been proprietary and therefore to manufacture equipment you would need to consider any patents or intellectual property rights. dPMR is an ETSI, royalty-free open standard and that provides the framework for ensuring interoperability of equipment by different manufactures to the same standard.’
Although there is potential for the emergence of different technical options to sow confusion in the minds of users, each technology has clear differences and will be suitable for specific types of users. In fact, when each proposition has become crisper and more clearly standardised, users will have a vastly increased menu of technical options to choose from.
‘It is exactly that,’ says Motorola’s Clark. ‘The needs of a customer choosing TETRA are very different to a customer that chooses DMR. Features such as encryption of mobile data and data speed are features a public safety organisation will need and insist upon, but it does come at a higher price point so commercial customers might go for a lower cost solution. There are discrete end customers with different needs.’
dPMR (digital private mobile radio) is an open ETSI standard that has also evolved from its first iteration as a PMR446 digital technology.
As with comparable technologies, notably DMR, there are tiers of functionality with dPMR. These are known as models within the dPMR development community:
Mode 1 is for licensed, peer-to-peer communications
Mode 2 is for base station and repeater use
Mode 3 is for multi-site, wide area networked systems
There is also the dPMR446 licence-free mode of dPMR.
Ian Lockyer (left), marketing manager at Icom UK, explains the history behind dPMR and its potential applications. ‘dPMR is a digital radio protocol that provides highly functional solutions by utilising low cost and low complexity technology,’ he says.
‘dPMR transmission is FDMA with a channel bandwidth of 6.25kHz. Only one 6.25kHz frequency allocation is required for voice communications. Where a 12.5kHz channel is allocated the other 6.25kHz can be re-used for another voice channel. dPMR is 100% digital and offers many forms of voice and/or data applications.
'It is an ideal platform for those radio users who need to migrate from analogue. dPMR Mode 3 is a collaboration between Icom and Fylde Micro and offers business users an immediate migration path from MPT to dPMR without the requirement of any MPT operation in the digital terminals.’
Digital mobile radio (DMR) is a digital radio standard specified for professional mobile radio (PMR) users and developed by ETSI.
DMR Tier I: Unlicensed
DMR Tier I products are for license-free use in the 446MHz band. Tier I provides for consumer applications and low-power commercial applications
DMR Tier II: Conventional
DMR Tier II covers licensed conventional radio systems, mobiles and hand portables operating in PMR frequency bands from 66-960MHz. DMR Tier II standard is targeted at users who need spectral efficiency, advanced voice features and integrated IP data services in licensed bands for high-power communications.
DMR Tier III: Trunked
DMR Tier III covers trunking operations in frequency bands from 66-960MHz. The Tier III standard specifies two-slot TDMA in 12.5kHz channels. Tier III supports voice and short messaging handling similar to MPT-1327 with built-in 128 character status messaging and short messaging with up to 288 bits of data in a variety of formats. It also supports packet data service in a variety of formats, including support for IPv4 and IPv6.
China’s PDT infrastructure
PDT (police digital trunking) is the wireless communications standard for China’s police. It was established by China’s major vendors of professional wireless communications equipment under the leadership of Information and Communications Bureau of the Chinese Ministry of Public Security. PDT is an open standard to vendors. Hytera Communications is the major contributor to the standard, and is the first vendor to launch a PDT two-way radio system.
GS Kok, VP of the public security and safety department at Hytera, explains: ‘In China when we built up to the Beijing Olympics, the Government was shocked at the infrastructure costs and thought TETRA was too expensive,’ he says. ‘The majority of rich cities in China already have TETRA so the police will continue to use it, but for new build and other regions China will use PDT which is loosely based on DMR.’
Ian Lockyer, marketing manager at Icom, feels little is known about the technology outside China and doesn’t see great prospects for the technology outside its home market. ‘I think all manufacturers and the industry in general will be analysing how PDT works and how it is being adopted in a rapidly developing Chinese economy,’ he says. ‘I think there will be limited interest in adopting this in the West because of technological and cultural differences. The market dominance of the main manufacturers will be a barrier for it ever to be considered.’